Welcome

The title says it all: this blog features physics videos found everywhere on the web: animations, demonstrations, lectures, documentaries.

Please go here if you want to suggest other nice physics videos, and here if I mistakingly infringed your copyrights. If you understand French, you'll find a huge selection of physics videos in French in my other blog Vidéos de Physique.

How do magnets work? Why do they attract and repel at long distances? Is it magic? No... it's quantum mechanics, and a bit more, as we explain in this, the longest MinutePhysics video ever.

Magnetism seems like a pretty magical phenomenon. Rocks that attract or repel each other at a distance - that's really cool - and electric current in a wire interacts in the same way. What's even more amazing is how it works. We normally think of special relativity as having little bearing on our lives because everything happens at such low speeds that relativistic effects are negligible. But when you consider the large number of charges in a wire and the strength of the electric interaction, you can see that electromagnets function thanks to the special relativistic effect of length contraction. In a frame of reference moving with the charges, there is an electric field that creates a force on the charges. But in the lab frame, there is no electric field so it must be a magnetic field creating the force. Hence we see that a magnetic field is what an electric field becomes when an electrically charged object starts moving.

This short video features commentary by David Sibeck, project scientist for the THEMIS mission, discussing a visualization of reconnection fronts.

Taking advantage of an unprecedented alignment of eight satellites through the vast magnetic environment that surrounds Earth in space, including NASA's ARTEMIS and THEMIS, scientists now have comprehensive details of the energy's journey through a process that forms the aurora, called a substorm.
Their results showed that small events unfolding over the course of a millisecond can result in energy flows that last up to half an hour and cover an area 10 times larger than Earth.

Trying to understand how gigantic explosions on the sun can create space weather effects involves tracking energy from the original event all the way to Earth. It's not unlike keeping tabs on a character in a play with many costume changes, because the energy changes form frequently along its journey: magnetic energy causes eruptions that lead to kinetic energy as particles hurtle away, or thermal energy as the particles heat up. Near Earth, the energy can change through all these various forms once again.

Most of the large and small features of substorms take place largely in the portion of Earth's magnetic environment called the magnetotail. Earth sits inside a large magnetic bubble called the magnetosphere. As Earth orbits around the sun, the solar wind from the sun streams past the bubble, stretching it outward into a teardrop. The magnetotail is the long point of the teardrop trailing out to more than 1 million miles on the night side of Earth. The moon orbits Earth much closer, some 240,000 miles away, crossing in and out of the magnetotail.

Tuesday, 24 September 2013

Comet ISON (C/2012 S1) may become a dazzling sight as it traverses the inner solar system in late 2013. During the weeks before its Nov. 28 close approach to the sun, the comet will be observable with small telescopes, and binoculars. Observatories around the world and in space will track the comet during its scorching trek around the sun. If ISON survives its searing solar passage, which seems likely but is not certain, the comet may be visible to the unaided eye in the pre-dawn sky during December.

This animation shows two views of comet ISON's path through the inner solar system. The first is a view following the comet along its orbit. The second is a view perpendicular to ISON's orbit.
Like all comets, ISON is a clump of frozen gases mixed with dust. Often described as "dirty snowballs," comets emit gas and dust whenever they venture near enough to the sun that the icy material transforms from a solid to gas, a process called sublimation. Jets powered by sublimating ice also release dust, which reflects sunlight and brightens the comet.

Friday, 20 September 2013

The free fall of a coin and feather are compared, first in a tube full of air and then in a vacuum. With air resistance, the feathers fall more slowly. In a vacuum, the objects fall at the same rate independent of their respective masses.

The audience will first be exposed to experimental results on electrons/photons that require for their explanation very counter-intuitive concepts, such as being here and there or spinning up and down at the same time, underlying quantum physics. Very special visual analogs will be used --- analogies are always useful to comprehend new in terms of known --- to comfort the intellectual paralysis of our (predisposed) mind in understanding the co-existence of mutually exclusive attributes in the microscopic quantum world.

Dr. Natthi Sharma is professor of physics at Eastern Michigan University since 1986.

Sunday, 15 September 2013

Neutrinos are elusive particles that are difficult to study, yet they may help explain some of the biggest mysteries of our universe. Using accelerators to make neutrino beams, scientists are unveiling the neutrinos' secrets.

A double cone is placed on the bars of an inclined plane. Instead of rolling down the plane the cone rolls up. Although the plane slants upward, the bars diverge so that the rotational axis of the cone, which passes through the center of mass, actually moves downward.

Sometimes, Earth mimics a supernova, producing a Terrestrial Gamma-ray Flash from the tops of thunderstorms. A new lightning sensor on the International Space Station could solve the mystery of these energetic bursts.

Wednesday, 11 September 2013

Reviews the operation of parallel RC circuit and specifically points out how to solve for branch currents and total impedance by using ohm's law. Reviews vector representations and show how approximate total current and phase angle are found by measuring the vectors. Introduces trigonometric functions used to solve for total impedance, total current, phase angle, and power factor. Concludes with a brief review of apparent and true power and their relationship to the power factor.

A mass hangs from two identical springs. First, the springs are attached in series by a short string between them. The springs are also connected in parallel by two peripheral strings that are initially slack. The center string is cut, changing the system from series to parallel. The mass does not move downwards, as one might have thought. Rather, the mass moves upwards because the spring constant of the system is increased.

Sunday, 8 September 2013

The Walkie Talkie, or Walkie Scorchie (?), is a new building in London which has been reflecting light in a rather hazardous way!
The Sky Mirror is a sculpture at the Nottingham Playhouse.
This video features Professor Mike Merrifield from the University of Nottingham.

LLCD will be NASA's first-step in creating a high performance space-based laser communications system.

The LLCD mission consists of space-based and ground-based components.

The Lunar Laser Space Terminal (LLST) is an optical communications test payload to fly aboard the LADEE Spacecraft and it will demonstrate laser communications from lunar orbit.

The ground segment consists of three ground terminals that will perform high-rate communication with the LLST aboard LADEE. The primary ground terminal, the Lunar Laser Ground Terminal (LLGT) is located in White Sands, NM and was developed by MIT/Lincoln Laboratory and NASA.

The ground segment also includes two secondary terminals located at NASA/JPL's Table Mountain Facility in California and the European Space Agency's El Teide Observatory in Tenerife, Spain.

The main goal of LLCD is proving fundamental concepts of laser communications and transferring data at a rate of 622 megabits per second (Mbps), which is about five times the current state-of-the-art from lunar distances. Engineers expect future space missions to benefit greatly from the use of laser communications technology.

Imagine two aliens racing across outer space to their moon. Who can we deem the fastest alien? With DIRT -- or the equation Distance = Rate x Time -- we can calculate their rates, using the distance they traveled and the time they took. Heather Tunnell explains how to use this helpful equation to determine which of our alien friends is truly faster.

"The Art of Science Learning" is an exciting project funded by the National Science Foundation that seeks to spark innovation and creativity in science education through the integration of art-infused learning methods. The Museum of Science and Industry, Chicago, is one of only three Incubators for Innovation nationwide that will be implementing and testing a new innovation curriculum which uses the arts to energize creative thinking and critical analysis.

Friday, 6 September 2013

US Department of Defense 1972
Reviews the use of vector analysis, pythagorean theorem, and trogonometric functions as applied to a series RC ciruit. Graphically illustrates the consruction of the impedance and voltage vector. Shows use of Ohm's law for AC to solve for unknown circuit parameters. Uses an oscilloscope to demonstrate phase relationships and relative amplitudes.

The deceptively simple wire coil that proves incredibly useful in the world of electronics - the inductor's ability to store energy in an electromagnetic field is the key to making transformers, electromagnets, and many more components. It truly is an awesome device!

Thursday, 5 September 2013

The Earth is 4.6 billion years old -- but how can humans relate to a number so colossal, and where do we fit on the geologic timeline? Comparing the Earth's lifetime to one calendar year, events like the extinction of dinosaurs and Columbus setting sail took place relatively recently. Joshua M. Sneideman reminds us of our time and place in the universe.

In 1916, Einstein -- as a consequence of his new theory of gravity -- predicted
the existence of gravitational radiation (ripples in the fabric of space--time
that propagate at the speed of light).

Today, the hunt for such gravitational waves has sparked a new field of fundamental and instrumental science, using kilometre-sized telescopes that exploit laser technology.
These new instruments are now in operation and close to observing Einstein's prediction for the very first time.

The observation of gravitational waves has the potential to change dramatically our understanding of the universe; we will be able to "hear" some of the most violent events in cosmic history, including black holes colliding in the centre of galaxies and the first fraction of a second after the Big Bang.

Tuesday, 3 September 2013

A NASA spacecraft slated for launch in September will fly to the Moon to investigate the tenuous lunar atmosphere. Researchers hope "LADEE" will solve a mystery that has been puzzling them since the days of Apollo.

In this setup, an interferometer is used to measure the wavelength of laser light. The incident beam is split into two paths, recombined, and projected on a screen. When one of the path lengths is varied, the interference pattern on the screen changes. By measuring the distance that a path length must be changed in order to achieve the original interference pattern, one can determine the wavelength of the incident light.

Einstein's equation E = mc2 is often said to mean that energy can be converted into matter. More accurately, energy can be converted to matter and antimatter.

During the first moments of the Big Bang, the universe was smaller, hotter and energy was everywhere. As the universe expanded and cooled, the energy converted into matter and antimatter. According to our best understanding, these two substances should have been created in equal quantities. However when we look out into the cosmos we see only matter and no antimatter.

The absence of antimatter is one of the Big Mysteries of modern physics. In this video, Fermilab's Dr. Don Lincoln explains the problem, although doesn't answer it. The answer, as in all Big Mysteries, is still unknown and one of the leading research topics of contemporary science.